These unusual bubbling reefs are located in Kattegat off the coast of Denmark. Methane seeps into the shallow waters in the northern Kattegat off the Danish coast to form spectacular submarine landscapes - the 'bubbling reefs' - due to carbonate-cemented sandstone structures which are colonized by brightly coloured animals and plants.

Hans Christian Andersen has been working for some time to document these bubbling reefs, and offers us a fascinating glimpse in this special DiveFilm Podcast version of his documentary, "Bubbling Reefs."

His website on the reefs, TheBubblingReefs.com, garnered the prize for the best website in the promotional category at the World Festival for Underwater Pictures at Antibes, France.

To learn more about Hans and his work, please visit his website, Skawdiver.dk.